The removal of contaminants from natural resources is an ongoing, significant problem. Numerous tactics have been considered with various degrees of success. In U.S. patent application Ser. No. 09/972,296 filed on Oct. 2, 2001 and issued Dec. 16, 2003 as U.S. Pat. No. 6,664,298, which is owned by the Assignee of the present invention and incorporated in the present application by express reference thereto, a method was disclosed for delivering the reactant material to the contaminant in situ. A method incorporated the concept of either emulsification of the reactant or encapsulation of the reactant prior to its delivery to the contaminant in situ. The Method disclosed and claimed in patent application Ser. No. 09/972,296 has particular success in using a zero-valent metal emulsion containing metal particles, surfactant, oil and water in a method of enhancing dehalogenation of dense non-aqueous phase liquid (DNAPL) sources.
A second patent application, PCT/US 03/16610, was filed May 28, 2003, corresponding to U.S. patent application Ser. No. 10/449,907, also filed on May 28, 2003 and issued Mar. 7, 2006 as U.S. Pat. No. 7,008,964, which patent also is owned by the Assignee of the present invention and is incorporated into the present application by reference thereto. This second patent application is directed, among other features, to a zero-valent metal emulsion containing zero-valent metal particles doped with a catalytic metal to remediate halogenated aromatic compounds, such as polychlorinated biphenyls (PCBs), from natural resources, i.e., in the ground.
PCBs have been used in many industrial applications because of their robust physical and chemical properties such as their resistance to acids, bases and oxidation, their excellent dielectric characteristics and their thermal stability at high temperatures (up to 350° C.). PCBs were abundantly used as a stabilizer in paints in the late 1960s. When PCBs were released into the environment, they were sorbed to particulate matter that was then dispersed over large areas. PCBs can be introduced into the food chain by the uptake of contaminated soils by biota and humans can directly inhale or absorb PCBs by dermal contact. Although the United States Environmental Protection Agency (EPA) has banned the manufacture of PCBs since 1979, PCBs are still present in the environment posing possible adverse health affects to both humans and animals. In fact, PCBs can still be found in the paints located on NASA property at a number of the Centers. The PCB levels in painted structures on the Kennedy Space Center (KSC) have been documented to be as high as 31,000 ppm.
Currently, only land filling or smelting operations are available for complete treatment of ex situ structures containing PCBs. Sandblasting or water blasting operations can be utilized to remove contaminated coatings from structures; however, this material must also be thermally treated or land-filled in a Toxic Substances Control Act (TSCA) regulated landfill.
As will become clear here below, the present invention expands on the concept described in the previously cited applications to effectively treat PCBs found in painted structures or other ex situ facilities. For the reasons stated above, and for other reasons stated below that will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for alternative methods and compositions for the removal of PCBs from ex situ structures.